Rotary film sealing and severing head for thermoplastics

Abstract

A rotary film sealing and severing device for use with thermoplastic film for forming packages. The device includes a rotating anvil assembly and a counter-rotating film cutting assembly having a heated sealing and cutting knife. First and second liquid cooled clamping bars on either side of the knife hold the layers of film together while the film is being sealed and cut. Cooling the clamping bars prevents the film from adhering to the clamps and causes the layers of film to quickly fuse together and allows high speed operation by preventing separation of layers of film due to slow cooling.

What is claimed is: 
     
       1. A heat sealing and severing device for packaging articles in tubular thermoplastic, said device comprising: multiple anvil assemblies rotatable about a first rotational axis and having resilient anvil surfaces spaced from said first rotational axis;   film cutting assemblies rotatable about a second rotational axis parallel with said first rotational axis;   a pair of hollow clamping bars mounted on each of said cutting assemblies with said bars being spaced apart and with each of said bars being parallel with said second rotational axis;   a heatable knife mounted on each of said cutting assemblies with each of said knives mounted between said clamping bars with said knives parallel to said clamping bars and spaced apart from said clamping bars, said knives each having a knife edge which is directed away from said second rotational axis;   means for synchronously rotating said film cutting assemblies and said anvil assemblies to cause said clamping bars and said knife edges to contact said resilient anvil surfaces as said anvil assemblies and said film cutting assemblies rotate into a predetermined position about said first and said second axes; and   means for providing a cooling liquid to each of said hollow clamping bars.   
     
     
       2. A heat sealing and serving device as defined in claim 1 including spring means for biasing said clamping bars away from said second rotational axis causing said clamping bars to contact said anvil surface before said knife edge contacts said anvil surface as said anvil surface is rotated into a position nearest to said film cutting assembly. 
     
     
       3. A heat sealing and severing device as defined in claim 1 including a slick anvil surface to facilitate movement of said thermoplastic across said anvil surface. 
     
     
       4. A heat sealing and severing device as defined in claim 1 including means for heating said knife to seal portions of overlapped thermoplastic with said thermoplastic between said anvil assembly and said film cutting assembly, and to sever a portion of the thermoplastic which contains one article from an adjacent portion of the thermoplastic which contains another article. 
     
     
       5. A heat sealing and severing device as defined in claim 4 including spring means for biasing said clamping bars away from said second rotational axis causing said clamping bars to contact said anvil surface before said knife edge contacts said anvil surface as said anvil assembly is rotated into a position nearest to said film cutting assembly.